RENTON, Wash. — The Seattle Seahawks are about to find out how much losing at least one of their top cornerbacks means to their defense.

Brandon Browner has dropped the appeal of his suspension for using performance-enhancing substances and will miss the final four games of the regular season, the league announced Wednesday.

Browner’s loss leaves the Seahawks without a Pro Bowl cornerback whose size and physical play has flustered wide receivers for much of the past two seasons. Walter Thurmond, who was a starter for a short time during the 2011 season before suffering a leg injury, will take Browner’s spot.

Browner will be eligible to rejoin the team on Dec. 31 and will be able to play in the postseason should the Seahawks make the playoffs.

“I’ve thought all along that we are very fortunate to have Walter with some background that has started for us in the past,” Seattle coach Pete Carroll said. “He’s an excellent athlete. He played very well for us this last week and he’ll step right up into that mode.”

News broke after Seattle’s loss at Miami on Nov. 25 that Browner and fellow starting cornerback Richard Sherman were facing suspensions after testing positive for PEDs.

A day later, Browner’s agent, Peter Schaffer, said his client had no knowledge of how any banned substance got into his system, but he did not provide specifics on when an appeal might take place.

Messages left for Schaffer on Wednesday were not immediately returned. Sherman is going forward with his appeal and he can play while that is under way.

“I’m still not commenting about it, but I’m disappointed when we lose anybody by injury or whatever. These guys work so hard to be here and all of that and you come to rely on guys, and when you lose guys it’s always disappointing,” Carroll said. “But really where the focus goes for us is right to the guys who are stepping up.”

Browner has 44 tackles, three interceptions and six passes defensed this season. He is in his second season with the Seahawks after getting pulled from the Canadian Football League because he fit the mold of what Carroll wants: big, physical cornerbacks who can play man coverage.

He was voted as a Pro Bowl alternate in his first NFL season, and ended up playing in the game. Last season he had 54 tackles and six interceptions, two of which were returned for touchdowns.

Browner is the fourth Seahawks player to be suspended for a PED violation in the past calendar year, joining John Moffitt, Allen Barbre and Winston Guy.

“I’ve been disappointed about the whole situation, that it is something that he had to deal with it and we had to deal with it, but there is nothing we can do at this point,” Carroll said.

Thurmond has played in just one game in the past 13 months, that coming last week in Chicago when he took over as Seattle’s defensive back in nickel situations with veteran Marcus Trufant out with a hamstring injury. Thurmond played in six games and started three during the 2011 season before suffering a broken ankle at Cleveland.

Thurmond’s injury opened up a chance of Sherman, who has developed into one of the best cover cornerbacks in football.

“It felt like I hadn’t missed a step from where I was last year. I’m just trying to make progress and get better,” Thurmond said. “It’s really just being patient, just getting back to my technique and my form of where I was last year and continuing to get better each week.”

With the Seahawks still unsure whether Trufant will be back this week, rookie Jeremy Lane will get the first chance at being the Seahawks’ nickel cornerback.

Lane, a sixth-round pick out of Northwestern State in Louisiana, has yet to play a down on defense this year, but he has been a standout on special teams, especially in punt coverage. Behind Lane is second-year cornerback Byron Maxwell.

“We have some concern about it, but I also know we have forced them to compete with our best guys throughout the time and we’re always anticipating with the younger guys that they are going to have to play, so they’re ready to go,” Carroll said. “They are as ready as they can be.”

Carroll also announced that wide receiver Sidney Rice has cleared all concussion tests and is expected to play against Arizona. Rice took a shot from Major Wright on the game-winning touchdown in overtime in Chicago last Sunday.

Defensive end Red Bryant played against Chicago despite a foot injury and is expected to be able play versus Arizona. Carroll was also hopeful about linebacker Leroy Hill, who missed the Bears game with an ankle injury and was replaced by Malcolm Smith.